Preheat the oven to moderate 180°C (Gas Mark 4, 350oF).

Beat the butter with a wooden spoon until it is pale and soft. Gradually add the sugar and beat until the mixture is smooth and creamy. Sift in the flour, cinnamon and cocoa, a little at a time, until the mixture is a smooth paste. Beat in the vanilla.

Using your hands, roll teaspoonfuls of the paste into balls and place them on a well-greased baking sheet, leaving about 5 cm (2 in) between each one. Dip a fork in cold water and use the back of the prongs to flatten out the balls. Put the sheet into the oven and bake the cookies for 12 minutes. Remove from the oven and allow to cool for 5 minutes. Transfer to a wire rack to cool completely before serving.